Conventionally, cream solder is printed by a screen printing on the land of a printed wiring board on which electronic parts are to be mounted. As shown in FIG. 41, each of printers, generally indicated with a reference 300, used to print cream solder includes a transfer mechanism to bring a printed wiring board 301 while keeping it in horizontal position, a screen mechanism 303 provided opposite to the printed wiring board 301 being brought by the transfer mechanism 302, and a squeegee mechanism 304 to squeeze the cream solder from the screen mechanism 303 to the printed wiring board 301. First, the printed wiring board 301 is brought with one side thereof being directed opposite to the screen mechanism 303. When the printed wiring board 301 is brought to a predetermined position, the screen mechanism 303 is placed close to the printed wiring board 301, then the squeegee mechanism 304 is moved in the direction of arrow X in FIG. 41 to squeeze the cream solder to the printed wiring board 301. Thus the cream solder is printed on the printed wiring board 301.
To print cream solder on the land on the other side of the printed wiring board 301, first the printed wiring board 301 is inverted for the other side thereof to be opposite to the screen mechanism 303. Next, the printer 300 used to print cream solder on the one side of the printed wiring board 301 is used to print cream solder on the land on the other side of the printed wiring board 301 in a similar manner. However, in case the printer 300 once used to print cream solder on the one side of the printed wiring board is used again to print cream solder on the land of the printed wiring board, the screen mechanism 303 is replaced with a screen mechanism 303 having formed thereon a pattern prepared for the other side of the printed wiring board 301 to print cream solder, by screen printing, to the land on the other side of the board 301.
To print cream solder to either side of the printed wiring board 301 as in the above, a printer 300 has to be used for each side of the printed wiring board 301 in one pass, so that the electronics packaging system can hardly be designed more compact. Also, since cream solder has to be printed on each side of the printed wiring board 301 in one pass, the electronics packaging system can hardly package electronic parts with a further improved efficiency.
An electronics packaging system generally indicated with a reference 400 in FIG. 42 is used to mount electronic parts on a printed wiring board 401 having cream solder printed thereon as in the above. As shown in FIG. 42, the packaging system 400 includes a printer 402 to print cream solder on the land of a printed wiring board 401 by the screen printing, a placing unit 404 to place an electronic part 403 on the printed wiring board 401 having cream solder printed on the land thereof, and a reflow unit 405 to heat the printed wiring board 401 having the electronic part 403 placed thereon to melt the solder and thus solder the electronic part 403. In the packaging system 400 for the electronic parts 403, the printed wiring boards 401 are brought one after another while being held horizontally or laid on the transfer mechanism. The printed wiring board 401 is brought through the printer 402, placing unit 404 and reflow unit 405 located in the upper portion of FIG. 42 and has the electronic parts 403 placed on the first side thereof, and then inverted. Then, the printed wiring board 401 is brought through other printer 402, placing unit 404 and reflow unit 405 located in the middle portion of FIG. 42 and thus has electronic parts 403 mounted on the second side thereof.
As in the above, the electronics packaging system 400 needs the printer 402, placing unit 404 and reflow unit 405 to mount electronic parts 403 on the first side of the printed wiring board 401, and also the other printer 402, placing unit 404 and reflow unit 405 to mount electronic parts 403 on the second side of the printed wiring board 401. Further, the electronics packaging system 400 needs an inversion mechanism to invert the printed wiring board 401 having the electronic parts 403 soldered to the first side thereof. Thus, the electronics packaging system 400 can hardly be designed more compact and package the electronic parts 403 with a higher efficiency.
Next, the electronic parts placed on the printed wiring board are soldered by a solder reflow unit. The solder reflow unit used to solder the electronic parts includes a transfer mechanism to bring a printed wiring board while keeping it in horizontal position, a reflow furnace to heat the printed wiring board and melt the cream solder printed on the land of the printed wiring board, and a heating mechanism to heat the inside of the reflow furnace. The heating mechanism is disposed to face each main side of a printed wiring board brought held in horizontal position in order to heat the printed wiring board from above and below.
The printed wiring board first has electronic parts placed on one side thereof, and then brought into the reflow unit. The printed wiring board is heated in the reflow furnace of the reflow unit. The cream solder on the land is melted and then cooled, and thus the electronic parts are soldered. The printed wiring board having the electronic parts soldered to the one side thereof is inverted and has cream solder printed on the other side thereof, and then electronic parts are placed on the land. The printed wiring board is brought again into the reflow unit. The printed wiring board is heated in the reflow furnace of the reflow unit. The cream solder printed on the land on the other side is melted and cooled, an thus the electronic parts are soldered.
As in the above, to solder electronic parts to either side of a printed wiring board, soldering has to be done twice in the reflow unit. Thus, the soldering process can hardly be shortened further. Also, to solder electronic parts to either side of a printed wiring board, a reflow unit has to be provided for each side of the printed wiring board. Thus, the electronics packaging system can hardly be designed more compact.
In the conventional electronics packaging system, electronic parts are placed on a printed wiring board having been brought in horizontal position, namely, in laid position. More specifically, to mount electronic parts to either side of a printed wiring board, they are first placed on one side of the printed wiring board, then the printed wiring board is inverted, and electronic parts are placed on the other side of the printed wiring board.
As in the above, the process of mounting electronic parts can hardly be shortened further. Also, a placing unit has to be provided for either side of a printed wiring board. Thus, the electronics packaging system can hardly be designed more compact.